1. Introduction

　The purpose of this research is to clarify a human vocal mechanism from engineering viewpoints by reproducing the vocal movement using a talking robot, and to create the dynamic model. By using the mechanical talking robot, we could experiment human speech quantitatively. This model will lead to the production of cellular phones that can compress data by transmitting human vocal movement instead of human voices. Furthermore, the model will lead to developing medical training devices for vocally challenged people and learning devices for foreign languages.

2. History of Waseda Talker Series

2-1. WT-4 (Waseda Talker No.4) (in 2004)

We developed a new anthropomorphic talking robot WT-4 (Waseda Talker No.4) that improved on WT-3. WT-4 had a human-like body to make the communication with a human more easily, and consisted of the total DOF was 19. We constructed an autonomous control method of WT-4 to mimic continuous human speech sounds by auditory feedback. In this method, the trajectory of each robot parameter was controlled so that the acoustic parameters (pitch, sound power, formant frequencies that are resonant frequencies of the vocal tract and have the peak of the output spectrum, and the timing of the switch between voiced and voiceless sounds) generated from the robot were close to those of human speech sounds.

2-3. WT-6 (Waseda Talker No.6) (in 2006)

We produced a new anthropomorphic talking robot WT-6 (Waseda Talker No.6). WT-6 consisted of 1-DOF lungs, 5-DOF vocal cords and articulators (the 5-DOF tongue, 4-DOF lips, 1-DOF jaw, nasal cavity and 1-DOF soft palate), and could reproduce human-like articulatory motion; the total DOF was 17. The length of the vocal tract is about 180[mm] and almost same as an adult male's. WT-6 has independent jaw opening/closing mechanism and three-dimensional tongue and vocal cavity made of thromoplastic rubber Septon (R) by Kuraray. The vocal cord model was also improved by adding new pitch control mechanism.

We developed a new anthropomorphic talking robot WT-7 (Waseda Talker No.7) mimicking human biological structure. WT-7 consisted of vocal organs (the 4-DOF vocal cords and 1-DOF lungs) and articulators (the 7-DOF tongue, 1-DOF velum, 5-DOF lips, and 1-DOF jaw), and could reproduce human- like articulatory motion; the total DOF was 19.Vocal cords, tongue and face were made of thermoplastic rubber Septon (R) by Kuraray. This material is so flexible and stretchable. Vocal cord model was also improved by adding new pitch control mechanism. By adopting a new linkage mechanism, the tongue model could form 3D vocal tract shape more accurately than the previous 2D model.